package Q1;

import java.math.BigDecimal;
import java.math.RoundingMode;
import java.util.Scanner;

public class Main {

    public static void main(String[] args) {
        Scanner scanner = new Scanner(System.in);

        int n = scanner.nextInt();
        int m = scanner.nextInt();

        int num1 = 1;
        for (int i = n; i >= m; i--) {
            num1 *= i;
        }

        int num2 = 1;
        for (int i = m; i > 0; i--) {
            num2 *= i;
        }



        // 四舍五入保留四位小数
        BigDecimal bd = new BigDecimal((num1 * 0.1) / (num2 * 0.1) * Math.pow(0.8, m) * Math.pow(0.2, n - m));
        bd = bd.setScale(4, RoundingMode.HALF_UP);
        System.out.printf("%.4f", bd.doubleValue());
    }

}
